Static vacuum head gravity feed electrographic inker



United States Patent M 3,498,261 STATIC VACUUM HEAD GRAVITY FEED ELECTROGRAPHIC INKER Roy E. Uhlenberg, Mountain View, Calif., assignor to Varian Associates, Palo Alto, Calif., a corporation of California Filed July 20, 1967, Ser. No. 654,898 Int. Cl. 150% 5/02 US. Cl. 118-637 7 Claims ABSTRACT OF THE DISCLOSURE There is disclosed for use in electrographic recording apparatus including a charge retentive recording medium a gravity fed inking system comprising a pivotably supported ink reservoir in liquid communication with an inking slot past which the charge retentive recording medium is drawn for inking. In a first or raised position ink is permitted to flow from the reservoir to the inking slot and a vacuum head is created in the reservoir above the liquid to prevent ink from pouring out of the inking slot. In a second or lower position ink flows from the inking slot to the reservoir for storage. The motion of the reservoir maintains the electrographic toner in colloidal suspension. The inking slot geometry is such as to store suflicient liquid to ink a limited amount of area on the recording medium and prevent loss of the vacuum head when the reservoir is raised to its first position.

In the electrographic inker, an elongated inking slot is disposed over the surface of the electrographic recording medium to be inked such as, for example, a charge retentive surface ofelectrographic recording paper. Relative motion is obtained between the inking slot and the surface to be inked such that the image to be inked passes the inking slot. Electrographic toner is pulled from the ink suspension within the inking slot to the charge images on the recording medium for inking same. A liquid passageway is provided between the inking slot and an outlet in the reservoir which stores the electrographic toner. A pivotable support for the reservoir is provided. In a first position of the reservoir, the liquid ink, contained within the inking slot and the channel communicating between the reservoir and the inking slot, drains by gravitational feed into the reservoir. In a second position, the reservoir is elevated to a level above the inking slot such that the ink drains by gravitational feed from the reservoir via the liquid passageway to the inking slot, thereby filling the inking slot. In the second elevated position the liquid ink in the reservoir covers the outlet in a manner somewhat similar to the action of an inverted tumbler filled with liquid such that a void or vacuum head is created in the reservoir above the liquid level to restrict flow of ink to the inking slot to prevent the ink from pouring out of the inking slot. The inking slot also restricts the counterflow of air from the inking slot back through the liquid passageway to the reservoir to sustain the vacuum head in the reservoir. When the reservoir is pivoted from its first position to its second position the electrographic toner within the reservoir is agitated, thereby providing a mixing action to obtain an even distribution of the electrographic toner in the liquid ink. Suificient ink is stored within the inking slot and channel leading to the slot to ink a limited amount of area on the electrographic recording medium. When the image to be inked has been inked, the reservoir is returned to its lower position and the ink drains back I Heretofore, inking slots filled with ink at less than at- 3,498,261 Patented Mar. 3, 1970 mospheric pressure, i.e., with a vacuum head, have been employed for inking electrostatic images on electrographic recording mediums such as strips of electrographic paper. Such an apparatus is described and claimed in copending US. application Ser. No. 577,443 filed Sept. 6, 1966 and assigned to the same assignee as the present invention. In this prior art structure, a vacuum pump was provided for drawing a vacuum on the inking channel and the reservoir containing the ink such as to pull the ink into the inking slot from the reservoir. The vacuum pulled on the inking slot served to restrict the flow of ink from the inking slot to the recording medium being inked. Such an inker was suitable for continuous operation as well as for intermittent one-shot operation.

In certain electrographic devices, it i not necessary that the inker have the capability of supplying ink on a continuous basis to relatively long strips of recording medium. More specifically, in the case of electrographic cameras and electrographic fingerprinting devices, it is only necessary that the inker supply sufiicient ink to ink one image and then a substantial period of time may elapse before the inker is required to ink a second image. In such applications, it is desirable to provide an inker, operable on a more or less one-shot basis, which does not have the complexity of a vacuum pump and air bleeder valve for controlling the vacuum head on the inking reservoir and inking slot.

Summary of the present invention A principal object of the present invention is the provision of an improved inker for electrographic apparatus.

One feature of the present invention is the provision of an inker which supplies ink to the inking slot by gravitational flow and which provides its own static vacuum head by restricting the flow of air to the reservoir to fill the void created by the flow of liquid from the reservoir to the inking slot, whereby an extremely simple and inexpensive inker is obtained for intermittent operation.

Another feature of the present invention is the same as the preceding feature wherein the inker includes a pivotable support for the inking reservoir such that the reservoir may be pivoted from a first position wherein ink drains from the inking slot by gravitational flow into the inking reservoir to a second position wherein the reservoir is elevated above the level of the inking slot so that ink flows to the slot by gravitational flow creating the static vacuum head on the reservoir by the flow of ink to the inking slot and by restricting the counterflow of air from the inking slot to the void created above the ink level in the reservoir.

Another feature of the present invention is the same as any one or more of the preceding features wherein a spring bias means is provided for holding the inking slot against the charge retentive surface of the recording medium to be inked, whereby uniform inking of the recording medium is obtained in use.

Another feature of the present invention is the same as any one or more of the preceding features wherein the inking head containing the slot is pivotably supported such that the inking slot and head may be pivoted away from the recording medium to facilitate access to the recording medium for threading the recording medium through the inking apparatus.

Other features and advantages of the present invention will become apparent upon a perusal of the following specification taken in conjunction with the accompanying drawings wherein:

Brief description of the drawings FIG. 1 is a side elevational view, partly in section, showing the inking apparatus of the present invention, and

FIG. 2 is a sectional view of the structure of FIG. 1 taken along lines 22 in the direction of the arrows.

Description of the preferred embodiments Referring now to FIGS. 1 and 2, there is shown the inking apparatus of the present invention. In the inking apparatus, an electrographic recording medium 1 such as a web of electrographic recording paper having a charge retentive surface 2 is threaded over a drive roller 3 which is knurled on its surface at 4 to grip the paper 1 and to pull the paper past an inking slot 5 provided in an inking head structure 6. The recording medium 1 has a charge image 7 deposited on the charge retentive surface 2 to be inked. As the charge image 7 comes under the inking slot 5, electrographic toner particles in colloidal suspension in a dielectric liquid (ink) are pulled from the ink within the inking slot 5 and are deposited upon the charge image 7 for developing (inking) saine.

Ink is supplied to the inking slot 5 from an ink reservoir 8 via a liquid passageway 9 communicating between the inking slot 5 and the ink reservoir 8. The ink reservoir 8 is pivotably mounted about pivot axis 11. Ink reservoir 8 is pivotable, from a first lower position B to a raised upper position A, about the pivot axis 11. In the lower position B, the ink drains from the inking slot 5 through the inking channel 9 into the reservoir 8 by gravity flow. In the raised position A, the ink drains from the reservoir 8 to fill the inking channel 9 and inking slot 5, causing the level of the ink within the reservoir to drop to a level indicated at 12. The ink which flows from the reservoir 8 into the inking channel 9 and slot 5 causes a partial vacuum head to be produced in the inking reservoir 8 above the liquid level 12. This region of partial vacuum is designated at 13. When the reservoir 8 is pivoted from the lower position B to the upper position A and the ink flows into the channel 9 and inking slot 5, a few bubbles of air will counterflow through the channel 9 into the reservoir '8 and will pass through the liquid to the void 13. This counterflow of air is not sufficient to cause the pressure within the void 13 to reach atmospheric pressure; thus, void 13 maintains a partial vacuum and provides a static vacuum head above the column of liquid ink filling the bottom portion of the reservoir 8, inking channel 9 and inking slot 5. The inking slot 5 is relatively narrow as of 0.063 in width and as of 2.5 in length to provide a restriction for the counterflow of air from the inking slot 5 into reservoir 8.

Also, as the reservoir 8 is pivoted from the lower position B to raised position A, the ink is agitated for mixing of the ink to prevent settling of the toner particles, thereby maintaining the particles in suspension. After the image 7 has been inked, the reservoir 8 is pivoted from the upper position A to lower position B and the ink drains from the inking slot 5 and channel 9 into the reservoir 8.

The inking head 6 is separately pivotable with respect to the inking reservoir 8 by means of a rotary seal 15 provided in the inking channel 9. More specifically, inking head 6 includes a cylindrical bore 16 which receives a tubular member 17 Which is affixed to the reservoir 8, to rotate with the reservoir 8. A rubber 'O-ring 18 is retained within a groove in the outer periphery of the tube 17 and forms a seal with the wall of bore 16 in the head 6.

A leaf spring 19 is affixed at one end to a cover plate 21 and bears at its other end 22 against the inking head 6 for holding the inking head against the charge retentive surface 2 of the recording medium 1. An idler roller 23 is also afiixed to the cover 21 and serves to hold the recording medium 1 against drive roller 3. When it is desired to thread the recording medium 1 over the drive roller 3, the cover 21 is removed and the inking head 6 is pivoted about pivot axis 11 away from the drive roller 3 to facilitate access to the drive roller 3 and to permit threading of the recording medium 1 over the drive roller 3.

The reservoir 8 includes a bottle 25 provided with threads at its open end 26 for threading into a cap member 27. An O-ring 28 is provided in the cap structure 27 to seal the bottle 29 to the cap 27 A central aperture 29 is provided in the cap to provide an outlet for the reservoir 8 and to provide a liquid communication path'between the reservoir 8 and the liquid channel 9. The central bore 9 in the tube 17 is blocked off at 31 and the tube 17 is supported in two pivotable bearing assemblies 32 and 33 in brackets 34 and 35, respectively. The brackets 34 and 35 are affixed to a housing 36 which contains the drive motor, not shown, and other apparatus for deposit ing charge images 7 upon the recording medium 1. The drive motor, not shown, is disposed in the housing 36 below the drive roller 3 and the motor serves to drive the drive roller 3 by a chain linkage 38 and sprocket 39.

In operation, the reservoir bottle 25 is filled with liquid electrographic toner to a level near the top thereof and the bottle is screwed into the cap 27 when it is in the position B. The charge image 7 is deposited upon the recording medium 1. The operator then pivots the reservoir 8 from position B to position A, thereby filling the channel 9 and inking slot 5 by gravity from the reservoir 8 in the raised position A. The drive motor is then actuated to drive the recording medium 1 past the inking slot 5 for inking of the image. After the image has been inked, the drive motor is de-energized, the inked image is then severed from the recording medium 1 by tearing the recording paper 1 against a serrated knife-like member, not shown. The reservoir 8 is then pivoted to the lower position B and the ink drains from inking slot 5 and channel 9 into the reservoir 8. The inking apparatus of the present invention is particularly adapted for one-shot operation such as those encountered in electrographic cameras and electrographic fingerprinting devices where only a limited amount of ink is required for inking each successive image on an intermittent basis.

Although the inking apparatus of FIGS. 1 and 2 has been shown and described as employing a pivotable support, this is not a requirement. Also, it is envisaged that other means may be employed for providing the fluid passageway between the reservoir 8 and the inking slot 5 which will permit inversion of the reservoir 8. For example, flexible tubing may be employed interconnecting the reservoir 8 to the inking slot 5 such that the operator could invert the reservoir for filling the inking slot and providing the static vacuum head on the reservoir. Also, the reservoir could be fixed in position above the level of the slot and valves provided for valving the fluid from the reservoir to the slot while maintaining an inlet to the reservoir closed to provide the vacuum head. In this latter case, means are preferably provided for stirring the liquid within the reservoir to prevent settling of the electrographic toner.

What is claimed is:

1. In an electrographic apparatus, means forming a container serving as a reservoir for liquid electrographic toner, means forming a structure having an inking slot, means providing a liquid passageway between said inking slot and an outlet in said reservoir for supplying liquid toner to said inking slot, means for producing relative motion between a charged retentive surface of a recording medium to be inked and said inking slot to cause the charge retentive surface of the recording medium to pass by said slot in liquid communication therewith for pulling toner particles out of saidslot to the charge image on the recording medium for inking same, the improvement comprising, means for providing gravitational flow of liquid toner from said outlet in said reservoir to the level at which the toner flows from said inking slot to the surface being inked, the flow of toner from said reservoir creating a void above the liquid level in said reservoir, and means for restricting the flow of air into the void above the liquid level in said reservoir to provide a restricted gravity flow of toner from said reservoir to the surface being inked to prevent flooding of the surface being inked, and wherein said means for providing gravitational flow from said reservoir includes a pivotable support for said reservoir, said reservoir being pivotable about said support between a first position and a second position such that in said first position gravitational flow of liquid toner is provided through said passageway from said inking slot to said reservoir for draining said inking slot into said reservoir, and in said second position liquid toner covers said outlet in said reservoir and liquid toner flows by gravity from said reservoir to said inking slot as restricted by counterflow of air through said liquid passageway and liquid covered reservoir outlet to the void created above the liquid level in said reservoir.

2. In an electrographic apparatus, means forming a container serving as a reservoir for liquid electrographic toner, means forming a structure having an inking slot, means providing a liquid passageway between said inking slot and an outlet in said reservoir for supplying liquid toner to said inking slot, means for producing relative motion between a charged retentive surface of a recording medium to be inked and said inking slot to cause the charge retentive surface of the recording medium to pass by said slot in liquid communication therewith for pulling toner particles out of said slot to the charge image on the recording medium for inking same, the improvement comprising, means for providing gravitational flow of liquid toner from said outlet in said reservoir to the level at which the toner flows from said inking slot to the surface being inked, the flow of toner from said reservoir creating a void above the liquid level in said reservoir, and means for restricting the flow of air into the void above the liquid level in said reservoir to provide a restricted gravity flow of toner from said reservoir to the surface being inked to prevent flooding of the surface being inked, and wherein said structure containing said inking slot is pivotably supported over the charge retentive surface to be inked, whereby said inking slot is movable away from the recording medium to facilitate access to the recording medium.

3. In an apparatus for flowing liquid on a medium, means forming a container serving as a reservoir for a liquid, means forming a structure having a slot, means providing a liquid passageway between said slot and an outlet in said reservoir for supplying the liquid to said slot, means for producing relative motion between the medium and said slot to cause the medium to pass by said slot in liquidcommunication therewith for pulling the liquid out of said slot to the medium, the improvement comprising, means for providing gravitational flow of liquid from said outlet in said reservoir to the level at which the liquid flows from said slot to the surface being coated, the flow of liquid from said reservoir creating a void above the liquid level in said reservoir, and means for restricting the flow of air into the void above the liquid level in said reservoir to provide a restricted gravity flow of liquid from said reservoir to the surface being coated to prevent flooding of the surface being coated, and wherein said means for providing gravitational flow from said reservoir includes a pivotable sup port for said reservoir, said reservoir being pivotable about said support between a first position and a second position such that in said first position gravitational flow of liquid is provided through said passageway from said slot to said reservoir for draining said slot into said reservoir, and in said second position liquid covers said outlet in said reservoir and liquid flows by gravity from said reservoir to said slot as restricted by counterflow of air through said liquid passageway and liquid covered reservoir outlet to the void created above the liquid level in said reservoir.

4. In an apparatus for flowing liquid on a medium, means forming a container serving as a reservoir for a liquid, means forming a structure having a slot, means providing a liquid passageway between said slot and an outlet in said reservoir for supplying the liquid to said slot, means for producing relative motion between the medium and said slot to cause the medium to pass by said slot in liquid communicaton therewith for pulling the liquid out of said slot to the medium, the improvement comprising, means for providing gravitational flow of liquid from said outlet in said reservoir to the level at which the liquid flows from said slot to the surface being coated, the fiow of liquid from said reservoir creating a void above the liquid level in said reservoir, and means for restricting the flow of air into the void above the liquid level in said reservoir to provide a restricted gravity flow of liquid from said reservoir to the surface being coated to prevent flooding of the surface being coated, and wherein said structure containing said slot is pivotably supported over the surface of the medium to be coated, whereby said slot is movable away from the medium to facilitate access to the medium, and including means for springbiasing said structure containing said slot against the surface of said medium to be coated.

5. The apparatus of claim 2 including means for spring-biasing said structure containing said inking slot against the surface of said recording medium to be inked.

6. The apparatus of claim 1 including means forming a rotary liquid passageway between said inking slot and said pivotable reservoir to permit relative rotary movement between said reservoir and said inking slot.

7. The apparatus of claim 3 including, means forming a rotary liquid seal in said liquid passageway between said slot and said pivotable reservoir to permit relative rotary movement between said reservoir and said slot.

References Cited UNITED STATES PATENTS 1,609,218 11/1926 Storck 11s 401 3,276,424 6/1966 Marx et al. 118637 1,167,633 1/1916 Dennis 1l8415 3,094,914 6/1963 Smith -s9 3,143,056 8/1964 Limberger 95-89 FOREIGN PATENTS 1,022,708 3/1966 Great Britain.

PETER FELDMAN, Primary Examiner US. Cl. X.R. 

